Dear doctor

Patchy periods Q: My daughter started her periods at 11. She is now nearly 14 and still has gaps of three or even, on one occasion recently, six, months. She eats well, is a reasonable weight for her height, has a healthy sprinkling of spots, enjoys school and leisure. But she is concerned about it. Should she be?

A: Patchy periods in adolescence are usually nothing to worry about. The reason they're often irregular for the first couple of years is that the hormone surge required for ovulation doesn't happen every month. Gradually the hormones get their act together and your daughter will slip into regular periods. If you take her to your GP, be prepared to be asked whether she could be pregnant. A blood test and ultrasound scan would establish whether there is an underlying problem like polycystic ovaries which is essentially a long term hormonal disturbance that may require treatment in time.

Cold comfort Q: I'm 18 and have poor circulation which makes me constantly cold. Even on warm days my hands are blue and I am forced to wear several layers to keep warm. Jogging daily to alleviate the problem has proved unsuccessful. Is there a medical condition to explain my symptoms and what can be done to combat them?

A: It sounds as though you may have Raynaud's phenomenon in which the small blood vessels that supply the skin of hands and/or feet tend to overreact to cold. The blood vessels narrow in response to cold that makes the skin go white, then blue and feel cold and numb. As the blood vessels open again, the skin goes red and may feel prickly.

You can help prevent this uncomfortable sensation by keeping your whole body warm, and wearing mittens rather than gloves when it's cold. Smoking can exacerbate it - yet another good reason to quit. Biofeedback techniques in which you're taught to think your fingers warm can be excellent. Drugs which open the blood vessels, such as nifedipine, help in severe cases but may cause headaches and flushing. Amlodipine, a newer drug which is used to control high blood pressure, works just as well with fewer side effects.

Stress doubt Q: About two months ago, I bought an over-the-counter hypnotic tape in one of the large chain bookshops. The tape I chose had to do with stress and relaxation. And while I neither expected to be, nor have been (as far as I know), literally hypnotised, I have found the tape very helpful indeed and feel other readers might benefit from this method of relaxation as well. My feeling is, however, that there are other, better, such hypnotic tapes on the market. Or perhaps even tapes that are actually recommended by professionals for general use. But I don't have a clue what they are or where to find them. Can you help?

A: How wonderful that you've found something cheap, harmless, easy to use and effective to help counter stress and induce a sense of relaxation. What you have done is to condition yourself, so that your brain now associates the music on the tape with feeling relaxed. It can sometimes work the other way; if a particular song were playing on the radio while you were vomiting with food poisoning, that song may forever make you feel literally sick. It probably doesn't matter what's actually on the tape as long as it works for you. Mozart is currently enjoying a good medical press since a recent report that he wrote particularly calming music, as a response to his own agitated state. So any good recording of Eine Kleine Nacht Musik is probably your best bet.

Stuck in the middle Q: I have had difficulty eating and swallowing for two years. At first doctors prescribed antibiotics for stomach upsets. Then they gave me anti-depressants and said my symptoms were psychological. I've now changed GP and he sent me for a scan and found that my oesophagus is closed over and that I have achalasia, often preventing food and liquids from entering my stomach for many hours before trickling down and therefore I need an operation. What does the operation entail, what is this illness, why does it happen and has my long term health been permanently harmed?

A: Achalasia is a fairly rare condition, but eminently treatable. No one really understands why it happens, but in some people, like yourself, the waves of muscular contraction that normally propel food down the oesophagus (peristalsis) don't work and the opening from the oesophagus into the stomach won't open to let food in. This leads to difficulty in swallowing fluids and solids, regurgitation of undigested food shortly after a meal, heartburn after eating and weight loss in more severe cases. No one really knows what causes it, but it doesn't just get better on its own and may get worse. Because it's a mechanical problem, surgery is often the only long-term option.

There are three possible procedures that you might be offered. Injections of botulism into the muscle at the opening of the stomach via a tube inserted through the mouth (endoscope). This procedure works well but doesn't last long and is usually only offered to elderly or frail people. Cutting the muscle (myomectomy) is 80-90% successful and safe but may cause discomfort and is a fairly major operation. Inserting a deflated balloon down the oesophagus via an endoscope, then inflating it to stretch the opening into the stomach, is slightly less likely to succeed (around 60% success rate) but causes less discomfort and you recover more quickly.

Should I be fuming? Q: I cycle to and from work. It takes about 10 to 15 minutes each way, and there is usually very heavy traffic on the roads. Do you think that getting this exercise in very poor air should be a concern for me? If so, do you think that the masks are an effective barrier, and do you recommend any brand or model in particular?

A: As a cyclist myself, with about the same distance to travel through the fumes, I was intrigued by your question. A spokesman for the Cyclists' Tourist Club (CTC) confirms what I wanted to hear; namely that the health benefits of cycling outweigh the risk of injury by a factor of more than 20, and that cyclists are no more likely to inhale polluted air than pedestrians or motorists though we may be more aware of the smell and taste of the air as we breathe in and out more. In fact, we cyclists apparently empty our lungs more fully than more sedentary people, so are less likely to have a stagnant layer of muck in our lungs. Masks help a bit; look out for one with an activated charcoal filter. To join CTC, call 01483 417217.

 These answers are intended to be as full and accurate as possible, but should never be used as a substitute for visiting a doctor. If you have a question for Dr Robinson, email DRANN@dircon.co.uk or write to her c/o The Health Editor, The Guardian, 119 Farringdon Road, London EC1 3ER. She regrets she cannot enter into personal correspondence.